Light‐Induced Water Splitting with Hematite: Improved Nanostructure and Iridium Oxide Catalysis

Tilley, S. David; Cornuz, Maurin; Sivula, Kevin; Grätzel, Michaël

doi:10.1002/anie.201003110

Cited by 1,014 publications

(733 citation statements)

References 29 publications

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“…Tilley et al used a layer of IrO 2 nanoparticles ($2 nm diameter) on hematite photoanodes by electrodeposition, resulting in a cathodic shi in the onset potential from 1.0 V to 0.8 V vs. RHE. 59 Riha et al reported that cobalt oxide monolayers and partial monolayers were successfully coated on hematite photoanodes by an atomic layer deposition method. 41 A stable 100 mV cathodic shi in onset potential was achieved on the planar device, and an even higher cathodic shi of $200 mV was obtained on an inverse opal hematite scaffold.…”

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confidence: 99%

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Zheng

Spurgeon

et al. 2014

Energy Environ. Sci.

564

439

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An important approach for solving the world's sustainable energy challenges is the conversion of solar energy to chemical fuels. Semiconductors can be used to convert/store solar energy to chemical bonds in an energy-dense fuel. Photoelectrochemical (PEC) water-splitting cells, with semiconductor electrodes, use sunlight and water to generate hydrogen. Herein, recent studies on improving the efficiency of semiconductor-based solar water-splitting devices by the introduction of surface passivation layers are reviewed. We show that passivation layers have been used as an effective strategy to improve the charge-separation and transfer processes across semiconductor-liquid interfaces, and thereby increase overall solar energy conversion efficiencies. We also summarize the demonstrated passivation effects brought by these thin layers, which include reducing charge recombination at surface states, increasing the reaction kinetics, and protecting the semiconductor from chemical corrosion.These benefits of passivation layers play a crucial role in achieving highly efficient water-splitting devices in the near future. Broader contextSemiconductor interface is one of the most important components/regions in photoelectrochemical (PEC) water splitting devices. The serious surface charge recombination, slow charge transfer kinetics and the poor photoelectrochemical stability are the three main challenges for the practical PEC water splitting devices. Recently, the studies of constructing passivation layer onto the semiconductor to address these challenges have attracted increasing research attentions, due to the potential application of solar to chemical energy conversion. When these layers incorporated onto semiconductor surface, signicant changes of the interface would be found including charge transfer improvement, surface charge recombination, and chemical corrosion, etc. Although various strategies have been suggested for this surface modication, a synergetic effect must be achieved on an advanced photoelectrodes accounting for the improved solar-tohydrogen efficiencies. This review will shed light on the recent PEC water splitting work surface state passivation, corrosion retardation and charge transfer improvement in this passivation layer.

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confidence: 99%

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Zheng

Spurgeon

et al. 2014

Energy Environ. Sci.

564

439

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“…14,15 Si 4+ has been shown to be an effective n-type dopant in hematite photoanodes for water oxidation. [16][17][18] Despite this, the electronic properties of silicon-doped single crystal hematite have not been reported. Recently, Zhao et al 12 synthesized…”

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Synthesis, electronic transport and optical properties of Si:α-Fe₂O₃ single crystals

et al. 2016

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We report the synthesis of silicon-doped hematite (Si:a-Fe 2 O 3 ) single crystals via chemical vapor transport, with Si incorporation on the order of 10 19 cm À3. The conductivity, Seebeck and Hall effect were measured in the basal plane between 200 and 400 K. Distinct differences in electron transport were observed above and below the magnetic transition temperature of hematite at B265 K (the Morin transition, T M ). Above 265 K, transport was found to agree with the adiabatic small-polaron model, the conductivity was characterized by an activation energy of B100 meV and the Hall effect was dominated by the weak ferromagnetism of the material. A room temperature electron drift mobility of B10 À2 cm 2 V À1 s À1was estimated. Below T M , the activation energy increased to B160 meV and a conventional Hall coefficient could be determined. In this regime, the Hall coefficient was negative and the corresponding Hall mobility was temperature-independent with a value of B10 À1 cm 2 V À1 s À1. Seebeck coefficient measurements indicated that the silicon donors were fully ionized in the temperature range studied. Finally, we observed a broad infrared absorption upon doping and tentatively assign the feature at B0.8 eV to photon-assisted small-polaron hops. These results are discussed in the context of existing hematite transport studies.

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“…[1][2][3][4][5][6][7][8] Intense current research efforts have been aimed at optimizing PEC performance by controlling the hematite structure, morphology, and surface chemistry and understanding fundamental charge carrier dynamics. 2,3,7,9,10 Despite these efforts, little is known about the spectral signatures and dynamics of photogenerated electrons and holes in these electrodes under water oxidation conditions.…”

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confidence: 99%

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe2O3) electrodes

Huang

Lin

Xiang

et al. 2012

Energy Environ. Sci.

128

163

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The spectra and dynamics of photogenerated electrons and holes in excited hematite (a-Fe 2 O 3 ) electrodes are investigated by transient absorption (from visible to infrared and from femto-to microseconds), bias-dependent differential absorption and Stark spectroscopy. Comparison of results from these techniques enables the assignment of the spectral signatures of photogenerated electrons and holes. Under the pulse illumination conditions of transient absorption (TA) measurement, the absorbed photon to electron conversion efficiency (APCE) of the films at 1.43 V (vs. reversible hydrogen electrode, RHE) is 0.69%, significantly lower than that at AM 1.5. TA kinetics shows that under these conditions, >98% of the photogenerated electrons and holes have recombined by 6 ms. Although APCE increases with more positive bias (from 0.90 to 1.43 V vs. RHE), the kinetics of holes up to 6 ms show negligible change, suggesting that the catalytic activity of the films is determined by holes with longer lifetimes.

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Light‐Induced Water Splitting with Hematite: Improved Nanostructure and Iridium Oxide Catalysis

Cited by 1,014 publications

References 29 publications

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Synthesis, electronic transport and optical properties of Si:α-Fe₂O₃ single crystals

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe2O3) electrodes

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Light‐Induced Water Splitting with Hematite: Improved Nanostructure and Iridium Oxide Catalysis

Cited by 1,014 publications

References 29 publications

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Enhanced photoelectrochemical water-splitting performance of semiconductors by surface passivation layers

Synthesis, electronic transport and optical properties of Si:α-Fe2O3 single crystals

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe2O3) electrodes

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Synthesis, electronic transport and optical properties of Si:α-Fe₂O₃ single crystals